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Q&As
How can I Create Roof Ventilation?
We are using the Eco-slate, a synthetic slate that once fixed self-bonds forming a single skin. The ridge is part of this single skin. There are no battens and the tiles are fixed directly to OSB board. However the building inspector wants the roof ventilated (cold or warm design).
Due to the shape, only part of roof can be ventilated in the gable walls- the hipped section and low pitch are not possible. I feel I should be able to 'seal' the roof void? Is it possible to demonstrate no moisture loss from the habitable space into roof? Would I be able to use bat slate openings (but not one every 0.7 of a metre)? I'm trying to find a credible solution, as eco slate were unable to help.
Thank you,
Bernadette
One Answer
This is a difficult question and probably one where opinion varies. My own view is that the building inspector is right to ask for ventilation with a cold roof design but that the use of Ecoslate in a warm roof situation would probably not require it.
With a warm roof, using Ecoslate would be similar to using a single ply membrane with the key differences being the method of fixing and the pitch. In a cold roof situation it should be expected that vapour control layers will be imperfect and assume that some moisture laden air will get into the void, hence the need for ventilation.
I am sorry not to be of more help but those advising you would really need to understand the project in much more detail before being able to do so.
– Tim Doherty, Build It expert